n, k = map(int, input().split())
X = list(map(int, input().split()))
A = list(map(int, input().split()))

X.sort()

g = [[] for _ in range(n)]
for i in range(1, n):
    if X[i]-A[i]<= X[i-1]:
        g[i].append(i-1)
    if X[i-1]+A[i-1] >= X[i]:
        g[i-1].append(i)

#print(g)
from collections import deque
s = deque()
s.append(k-1)
visit = [0]*n
visit[k-1] = 1
while s:
    x = s.pop()
    for nx in g[x]:
        if visit[nx] == 0:
            visit[nx] = 1
            s.append(nx)
#print(visit)
print(sum(visit))